Occlusion device with flexible spring connector

ABSTRACT

An occlusion device includes a center assembly having a flexible section formed by a spring connector and a safety tether. The flexible spring connector gives the center assembly improved torque and flexure characteristics, which allows the occlusion device to better conform to the contours of the heart. The safety tether serves to further ensure the structural integrity of the center assembly.

BACKGROUND OF THE INVENTION

This invention relates to an occlusion device for repairing cardiovascular defects. More specifically, this invention relates to an occlusion device which has a center assembly including a flexible spring connector that provides improved torque and flexure characteristics and allows the device to better conform to the contours of the heart.

Normally, permanently repairing certain cardiac defects in adults and children requires open heart surgery, a risky, expensive, and painful procedure. To avoid the risks and discomfort associated with open heart surgery, occlusion devices have been developed that are small, implantable devices capable of being delivered to the heart through a catheter. Rather than surgery, a catheter inserted into a major blood vessel allows an occlusion device to be deployed by moving the device through the catheter. This procedure is performed in a cardiac cathlab and avoids the risks and pain associated with open heart surgery. These occlusion devices can repair a wide range of cardiac defects, including patent foramen ovale, patent ductus arteriosus, atrial septal defects, ventricular septal defects, and may occlude other cardiac and non-cardiac apertures. There are currently several types of occlusion devices capable of being inserted via a catheter. The occlusion devices must have sufficient flexibility to accomplish the sharp and numerous turns in the body's vasculature.

Another challenge in deploying an occlusion device in the heart is the variations of the contours of the aperture the occlusion device is meant to close. In particular, when occluding septal defects, the uneven topography in the vascular and septal walls of the human heart makes it difficult to design a device that can adapt to such variations. The challenge in designing an occluder which conforms to the uneven topography is compounded by the fact that the contours of each defect in each individual patient are unique. Poor conformation to the defect results in poor seating of the occlusion device across the aperture, which decreases the ability of the device to successfully occlude the aperture.

Lack of conformation to the walls of the heart can place significant amounts of stress on the occlusion device and decrease fatigue life. Once deployed, different parts of the occluder may experience more or less stress as a result of the uneven topography. At some point, stressed parts of the occluder may break. Broken parts increase the likelihood of damage to the surrounding tissue and lead to patient anxiety.

Another obstacle which may be encountered is the difficulty in readily distinguishing the individual occluder elements in order to determine their position in relation to each other and allow for repositioning, while still maintaining the flexibility needed for better conformation.

Thus, there is a need in the art for an occlusion device that will occlude cardiac defects and will match the contours of the heart thereby increasing the life of the device and its sealing ability while reducing damage to the surrounding tissue. There is also a need for an occlusion device that prevents rotation of the individual occluder elements around the center post, while still maintaining the needed flexibility to properly position the device and successfully match the contours of the heart.

BRIEF SUMMARY OF THE INVENTION

The present invention is an occlusion device having a center assembly that includes a flexible spring connector. The occlusion device has a first occluding body and a second occluding body connected by the center assembly. The center assembly comprises a proximal hub, which is attached to the first occluding body, a distal hub, which is attached to the second occluding body, and a flexible spring connector extending between the proximal hub and the distal hub. The flexible spring connector increases the ability of the occlusion device to more accurately conform to the defect, while still allowing the device to be moved, deployed and retrieved using a catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A-1B are diagrams of an occlusion device with a center assembly that includes a flexible spring connector being inserted into a defect.

FIG. 1C is a diagram demonstrating the conformation capabilities of the occlusion device of FIGS. 1A-1B.

FIG. 2 is a first embodiment of a center assembly for use in an occlusion device where the flexible spring connector is comprised of a single spring and a safety tether.

FIG. 3 is a partial cross sectional view of a second embodiment of a center assembly for use in an occlusion device where the flexible spring connector is comprised of a multi-filar spring and a safety tether.

FIG. 4 is a partial cross sectional view of a third embodiment of a center assembly for use in an occlusion device where the flexible spring connector is comprised of two oppositely wound, concentric springs and a safety tether.

DETAILED DESCRIPTION

FIG. 1A-1B illustrate how occlusion device 10 having flexible spring connector 16 is deployed. Occlusion device 10 includes proximal hub 12, distal hub 14, flexible spring connector 16, knob 18, proximal support frame 20 and proximal sheet 22 (which form proximal occluding body 26), distal support frame 28 and distal sheet 30 (which form distal occluding body 32), and atraumatic tips 34. Also, shown are septal wall S, septal defect D, catheter 36, and delivery forceps 38.

Flexible spring connector 16 extends between proximal hub 12 and distal hub 14 to form a center assembly. (Methods of attaching flexible spring connector 16 to proximal and distal hubs 12, 14 will be discussed in detail with reference to FIGS. 3-4.) Proximal and distal hubs 12, 14 and flexible spring connector 16 may be comprised of any suitable material, including Nitinol (a nickel-titanium alloy), titanium or stainless steel. All three components of the center assembly may be comprised of the same material to simplify the welding process for assembly purposes. Flexible spring connector 16 is preferably formed to have a diameter of less than about 5 millimeters. In addition, the length of flexible spring connector 16 is preferably less than about 20 millimeters.

Proximal and distal support frames 20, 28 are attached to sheets 22, 30 in any suitable manner, such as with sutures or by molding sheets 22, 30 directly around proximal and distal support frames 20, 28 to form proximal occluding body 26 and distal occluding body 32. Proximal and distal support frames 20, 28 may be comprised of any number of arms (although only one arm of each of frames 20 and 28 can be seen in FIG. 1). One method of connecting the arms to proximal and distal hubs 12, 14 is to provide proximal and distal hubs 12, 14 with drill holes through which the arms extend. Atraumatic tips 34 are located at the distal end of each arm and serve to minimize damage to the surrounding tissue. Atraumatic tips 34 provide a place for sutures to attach sheets 22, 30 to proximal and distal support frames 20, 28. One method of suturing sheets 22, 30 to proximal and distal support frames 20, 28 is to provide atraumatic tips 34 with drill holes through which sutures pass. In this way, sheets 22, 30 are sewn to support frames 20, 28 at atraumatic tips 34. Proximal support frame 20 is connected to proximal hub 12. Distal support frame 28 is connected to distal hub 14.

More specifically, occlusion device 10 is constructed so that proximal and distal support frames 20, 28 are easily collapsible about proximal and distal hubs 12, 14. Due to this construction, occlusion device 10 can be folded so that proximal and distal support frames 20, 28 are folded in an axial direction. Proximal and distal sheets 22, 30, which are attached to proximal and distal support frames 20, 28, are flexible, and can likewise collapse as proximal and distal support frames 20, 28 are folded. In addition, proximal hub 12 further comprises knob 18, which allows for occlusion device 10 to be grasped by forceps 38 as it is inserted into the body through catheter 36.

Once occlusion device 10 is deployed, support frames 20, 28 must serve to hold proximal and distal sheets 22, 30 in place to seal defect D. To ensure there is sufficient tension to hold sheets 22, 30 in place, support frames 20, 28 are made of a suitable material capable of shape memory, such as Nitinol. Nitinol is preferably used because it is commercially available, very elastic, non-corrosive, and has a fatigue life greater than that of stainless steel or titanium. To further ensure that support frames 20, 28 do not suffer from fatigue failures, support frames 20, 28 may be made of stranded wire or cables.

Sheets 22, 30 are comprised of a medical grade polymer in the form of film, foam, gel, or a combination thereof. One suitable material is DACRON®. Another suitable material is polyurethane. Preferably, a high density polyvinyl alcohol (PVA) foam is used, such as that offered under the trademark IVALON®. To minimize the chance of occlusion device 10 causing a blood clot, foam sheets 22, 30 may be treated with a thrombosis inhibiting material, such as heparin.

The size of sheets 22, 30 may vary to accommodate various sizes of defects. When measured diagonally, the size of sheets 22, 30 may range from about 10 millimeters to about 45 millimeters. In some instances, it may be desirable to form sheets 22, 30 so that they are not both the same size. For instance, one sheet and its associated fixation device can be made smaller (25 millimeters) than the corresponding sheet and its associated fixation device (30 millimeters). This is particularly useful in situations where occlusion device 10 is to be placed at a location in the heart which is close to other nearby cardiac structures. Making sheets 22, 30 different sizes may assist in providing optimal occlusion of a defect, without affecting other structures of the heart which may be nearby.

FIG. 1A illustrates occlusion device 10 being inserted into septal defect D, which is one example of a cardiac defect that may be occluded using occlusion device 10. Occlusion device 10 is being inserted into septal defect D from catheter 36. Occlusion device 10 is held by delivery forceps 38. To insert occlusion device 10, catheter 36 is positioned proximate septal defect D. Next, delivery forceps 38 is used to push occlusion device 10 through catheter 36 so that distal occluding body 32 unfolds in the left atrium. Although distal occluding body 32 has been deployed, proximal occluding body 26 is still folded in catheter 36.

The placement of catheter 36, or other means that guides occlusion device 10 to septal defect D, determines the location of and angle at which occlusion device 10 is deployed. Once catheter 36 is properly positioned at septal defect D, delivery forceps 38 is used to push occlusion device 10 through septal defect D. Distal occluding body 32 of occlusion device 10 is then allowed to expand against septal wall S surrounding septal defect D.

Spring connector 16 is flexible but remains inside catheter 36 and is therefore immobilized. If spring connector 16 of occlusion device 10 is not flexible (or flexible but immobilized), the center assembly must enter septal defect D following the same angle of insertion as catheter 36 or other delivery device. As a result, the insertion angle is limited by the catheter's angle of insertion.

Often, due to limited space, catheter 36 enters the heart at an angle that is not perpendicular to septal wall S. In this situation, occlusion device 10 cannot enter septal defect D properly because the line of the center assembly must follow the same line as catheter 36. Occlusion device 10 must be forced into septal defect D at an angle, which may cause the tissue surrounding septal defect D to become distorted. If the surrounding cardiac tissue is distorted by catheter 36, it is difficult to determine whether occlusion device 10 will be properly seated once catheter 36 is removed and the tissue returns to its normal state. If occlusion device 10 is not seated properly, blood will continue to flow through septal defect 32 and occlusion device 10 may have to be retrieved and re-deployed. Both doctors and patients prefer to avoid retrieval and re-deployment because it causes additional expense and longer procedure time.

FIG. 1B shows occlusion device 10 with flexible spring connector 16 being inserted into defect D. In FIG. 1B, occlusion device 10 has been further advanced through catheter 36 to expose flexible spring connector 16.

Because spring connector 16 is flexible, the insertion angle of occlusion device 10 is not restricted to that of catheter 36. Occlusion device 10 can be easily inserted, because once flexible spring connector 16 is outside catheter 36, the angle of insertion can be changed by allowing flexible spring connector 16 to move. This variable insertion angle allows occlusion device 10 to enter defect D at an optimum angle, minimizing distortion of surrounding cardiac tissue. If the tissue is not distorted when occlusion device 10 is deployed, the seating of occlusion device 10 should not change drastically once catheter 36 is removed. Because occlusion device 10 can be properly seated at the first insertion, the number of cases that require retrieval and redeployment should decrease.

FIG. 1C shows occlusion device 10, which is fully deployed and is occluding defect D. Shown is occlusion device 10, which includes proximal hub 12, distal hub 14, flexible spring connector 16, knob 18, proximal support frame 20 and proximal sheet 22 (which form proximal occluding body 26), distal support frame 28 and distal sheet 30 (which form distal occluding body 32), and atraumatic tips 34. Also, shown are septal wall S, septal defect D, catheter 36, and delivery forceps 38.

By forming at least a portion of the center assembly to include flexible spring connector 16, the seating ability of occlusion device 10 is improved without the need for increased arm tension, which is necessary to occlude septal defect D or functionality (i.e. ability to move through a catheter, to twist or turn during deployment, to place against a septal wall) needed to properly deploy occlusion device 10.

Flexible spring connector 16 has no negative effect on the ability to move occlusion device 10 through catheter 36. This is because the length of flexible spring connector 16 is preferably less than about 20 millimeters and also because when flexible spring connector 16 experiences pushing or pulling forces each coil exerts a force on an adjacent coil. As such, flexible spring connector 16 is sufficiently rigid when necessary, such as when proximal and distal hubs 12, 14 are pushed toward one another when occlusion device 10 is moved through catheter 36.

At the same time, flexible spring connector 16 is capable of flexure. When flexible spring connector 16 is not being pushed or pulled or is not experiencing resistance, flexible spring connector 16 is more flexible. This flexibility of spring connector 16 allows for occlusion device 10 to be moved easily through sharp turns in a catheter, and allows for occlusion device 10 to be placed so that one side of occlusion device 10 is easily flexible relative to the other side.

Further, once deployed, flexible spring connector 16 is strong enough to hold proximal and distal occluding bodies 26, 32 of occlusion device 10 in place. Thus, flexible spring connector 16 provides the functionality required to deploy occlusion device 10, while offering the benefits of a fully flexible center connector.

In FIG. 1C, distal occluding body 32 has been properly positioned, proximal occluding body 26 has been deployed and occlusion device 10 has been released. FIG. 1C also demonstrates the ability of occlusion device 10 with flexible spring connector 16 to conform to an irregularly shaped septal defect D.

Another important advantage of the present invention is that flexible spring connector 16 allows distal and proximal occluding bodies 26, 32 to conform more readily to the contours of a heart after it is deployed, providing a custom fit to a variety of defects. Often, when implanted, occlusion device 10 is located in an irregularly shaped defect. Having flexible spring connector 16 allows occlusion device 10 to conform to a broader spectrum of defects.

For instance, as viewed in FIG. 1C, septal wall S on the bottom of septal defect D may be only a few millimeters thick, but septal wall S on the top of septal defect D may be much thicker. In such cases, one side of occlusion device 10 may be bent open further than the other side. The side that is more distorted carries a high static load which increases pressure on the surrounding tissue and also increases the possibility of device fracture or septal tissue perforation. Because spring connector 16 is flexible, it can bend such that proximal and distal support frames 20, 28 need not be the only the only parts which adjust to fit septal defect D. The ability to conform to a variety of heart contours results in better seating, reduces arm tension (increasing fatigue life), and decreases the likelihood of damage to tissue resulting from device fracture.

Another feature of occlusion device 10 is that it is fully retrievable. To allow occlusion device 10 to be retrievable, as well as ensure that occlusion device 10 fits into a small diameter catheter, it is important to ensure that the arms of support frames 20, 28 are not of a length that results in atraumatic tips 34 clustering at the same location. If atraumatic tips 34 all cluster at the same location when occlusion device 10 is inside catheter 36, occlusion device 10 will become too bulky to allow it to be easily moved through catheter 36.

FIG. 2 is a first embodiment of center assembly 40 for use in an occlusion device. Center assembly 40 includes proximal hub 42, distal hub 43 and flexible spring connector 44, which comprises coils 46. Also shown is safety tether 47, grasping knob 48, and holes 49, which provide a location for attaching the occluding bodies, such as the wire support frames (shown in FIG. 1) to proximal and distal hubs 42, 43.

Flexible spring connector 44 extends between proximal hub 42 and distal hub 43 to form center assembly 40. (Methods of attaching flexible spring connector 44 to proximal and distal hubs 42, 43 will be discussed in detail with reference to FIGS. 3-4.) Proximal and distal hubs 42, 43 and flexible spring connector 44 may be comprised of any suitable material, including Nitinol, titanium or stainless steel. All three components of the center assembly may be comprised of the same material to simplify the welding process for assembly purposes. Flexible spring connector 44 is preferably formed to have a diameter of less than about 5 millimeters. In addition, the length of flexible spring connector 44 is preferably less than about 20 millimeters.

Flexible spring connector 44 is comprised of a single wire, which has a diameter of less than about 0.05 millimeters and comprises coils 46. Coils 46 of flexible wire connector 44 have an overall pitch of less than about 45 degrees and provide both the strength and flexibility needed to properly occlude a defect.

When flexible spring connector 44 is formed of Nitinol it may be subjected to a precise pre-shaping to give it a “shape-memory.” This shape memory helps to hold the coils 46 in place and can be used to add pre-tension to coils 46, so that coils 46 can return to their original shape even after the strong deformation that occurs when an occlusion device is passed through a catheter. Resulting flexible spring connector 45 is extremely flexible and also has an improved resistance to fatigue.

Safety tether 47 serves to further ensure the structural integrity of center assembly 40. Safety tether 47 connects proximal hub 42 to distal hub 43 and extends through the middle of flexible spring connector 44. Flexible spring connector 44 changes its shape in response to an external force. When a push force is applied to flexible spring connector 44, its movement is limited because coils 46 line up on each other and each coil exerts a force on an adjacent coil. When the push force is removed, flexible spring connector 44 returns to its original shape. In contrast, when a pull force is applied to flexible spring connector 44, coils 46 separate from each other and if enough force is applied flexible spring connector 44 will permanently deform and never return to its original shape. Safety tether 47 serves to limit the extension of flexible spring connector 44 by becoming taut when too much pull force is applied. In this way, safety tether 47 ensures that center assembly 40 remains fully connected while navigating the vasculature of a body and during deployment in a heart. Safety tether 47 also makes it possible to retrieve an occlusion device having flexible spring connector 44 because for retrieval to occur, the device must be pulled back through a catheter.

Safety tether 47 may be comprised of any suitable material, including Nitinol, titanium, stainless steel or polymeric material. In addition, safety tether 47 may be comprised of a single wire or thread or safety tether 47 may be comprised of a multi-wire strand or cable or a multi-thread fabric braid.

FIG. 3 is a partial cross sectional view of a second embodiment of center assembly 50 for use in an occlusion device. Center assembly 50 includes proximal hub 52, distal hub 53 and flexible spring connector 54, which comprises coils 56. Also shown is safety tether 57, grasping knob 58, holes 59, which provide a location for attaching the occluding bodies, such as the wire support frames (shown in FIG. 1) to proximal and distal hubs 52, 53, knots 60 and cavities 62P, 62D.

Flexible spring connector 54 extends between proximal hub 52 and distal hub 53 to form center assembly 50. Proximal and distal hubs 52,53 and flexible spring connector 54 may be comprised of any suitable material, including Nitinol, titanium or stainless steel. All three components of the center assembly may be comprised of the same material to simplify the welding process for assembly purposes. Flexible spring connector 54 is preferably formed to have a diameter of less than about 5 millimeters. In addition, the length of flexible spring connector 54 is preferably less than about 20 millimeters.

In the embodiment shown in FIG. 3, flexible spring connector 54 comprises a multi-filar spring having two wires, which each have an overall diameter of less than about 0.05 millimeters. Flexible spring connector 54 is formed by coiling two wires together simultaneously to form a multi-filar spring. Resulting spring connector 54 is extremely flexible and retains sufficient strength to properly occlude a defect. Although in FIG. 3, flexible spring connector 54 is comprised of a multi-filar spring having two wires, a multi-filar spring having any number of wires may be used. The flexibility of spring connector 54 would depend upon the number of wires used to form the multi-filar spring. In general, the flexibility decreases when the number of wires used to form a multi-filar spring is increased.

As shown in FIG. 3, center assembly 50 may be assembled by inserting proximal hub 52 and distal hub 53 onto flexible spring connector 54. This assembly method may be used to with all of the embodiments described with respect to the present invention. Proximal and distal hubs 52, 53 are provided with drill holes or cavities 62P and 62D, which are sized to correspond to an overall diameter of flexible spring connector 54. Proximal hub 52 is inserted onto a proximal end of flexible spring connector 54. Distal hub 53 is inserted onto a distal end of flexible spring connector 54. Proximal and distal hubs 52,53 may be secured to flexible spring connector 54 in any suitable manner. For instance, as shown, proximal and distal hubs 52, 53 are laser welded to flexible spring connector 54 at weld joints. Other assembly methods include crimping flexible spring connector 54 to proximal hub 52 and distal hub 53 or using a collar or pinto secure flexible spring connector 54 to proximal hub 52 and distal hub 53.

Given the nature of spring connector 54 and the manner in which it is attached to proximal and distal hubs 52, 53, spring connector 54 is extremely flexible, while retaining the ability to transmit torque, push, and pull forces. In addition to being capable of articulation, since flexible spring connector 54 is also capable of transmitting torque, it is possible to rotate an occlusion device including flexible spring connector 54 during deployment. This allows better positioning and seating of the occlusion device.

While it may be necessary to rotate the occlusion device during deployment, it is often not desirable for occluding bodies to be rotatable relative to center assembly 50 or to one another. When the occluding bodies are attached to proximal and distal hubs 52,53 (as described with respect to FIGS. 1A-1B), the occluding bodies will be prevented from rotating with respect to each other and to spring connector 54.

There are several disadvantages to allowing occluder elements to rotate around a center assembly. First, it is possible that the support arms of one support frame will line up with the arms of the other support frame, making it difficult to distinguish one set from the other set when the occlusion device is viewed on a fluoroscope. As a result, it is more of a challenge to determine the exact position of either support frame because when aligned, the two become indistinguishable.

Secondly, preventing rotation of the occluder elements may improve the overall positioning of the device. For example, when inserting a device that allows freedom of rotation, if upon the insertion of the device, the arms of a support frame are laying in an undesirable position, such as resting against the aorta, simply manipulating the device to reposition the arms may not be possible because the center assembly will spin relative to the occluder element, leaving the arms in the original position.

Finally, the preliminary loading of the device may be hindered if rotation of the support frames is not prevented. When the individual occluder elements spin and twirl, loading the occlusion device into a delivery device or catheter may be more difficult and time-consuming.

Center assembly 50 also includes safety tether 57. Safety tether 57 serves to further ensure the structural integrity of center assembly 50. Safety tether 57 connects proximal hub 52 to distal hub 53 and extends through the middle of flexible spring connector 54. Flexible spring connector 54 changes its shape in response to an external force. When a push force is applied to flexible spring connector 54, its movement is limited because coils 46 line up on each other and each coil exerts a force on an adjacent coil. When the push force is removed, flexible spring connector 54 returns to its original shape. In contrast, when a pull force is applied to flexible spring connector 54, coils 56 separate from each other and if enough force is applied flexible spring connector 54 will permanently deform and never return to its original shape. Safety tether 57 serves to limit the extension of flexible spring connector 54 by becoming taut when too much pull force is applied. In this way, safety tether 57 ensures that center assembly 50 remains fully connected while navigating the vasculature.

Safety tether 57 may be comprised of any suitable material, including Nitinol, titanium, stainless steel or polymeric material. In addition, safety tether 57 may be comprised of a single wire or thread or safety tether 57 may be comprised of a multi-wire strand or cable or a multi-thread fabric braid.

As shown in FIG. 3, safety tether 57 is attached to proximal and distal hubs 52 and 53 by threading it though a cavity in proximal and distal hubs 52 and 53 and securing safety tether 57 to an outside surface of proximal and distal hubs 52 and 53 with knots 60. However, safety tether 57 may be attached to proximal and distal hubs 52 and 53 with any suitable method. For instance, a crimp ring could also be used to attached safety tether 57 to proximal and distal hubs 52 and 53.

FIG. 4 is a partial cross sectional view of a third embodiment of center assembly 70 for use in an occlusion device. Center assembly 70 includes proximal hub 72, distal hub 73 and flexible spring connector 74. Flexible spring connector comprises inner spring 74 and outer spring 76. Also shown is safety tether 77, grasping knob 78, holes 79, which provide a location for attaching the occluding bodies, such as the wire support frames (shown in FIG. 1) to proximal and distal hubs 72, 73, knots 80 and cavities 82P, 82D.

Flexible spring connector 74 extends between proximal hub 72 and distal hub 73 to form center assembly 70. (Methods of attaching flexible spring connector 74 to proximal and distal hubs 72, 73 are identical to those discussed in detail with reference to FIG. 3.) Proximal and distal hubs 72, 73 and flexible spring connector 74 may be comprised of any suitable material, including Nitinol, titanium or stainless steel. All three components of the center assembly may be comprised of the same material to simplify the welding process for assembly purposes. Flexible spring connector 74 is preferably formed to have a diameter of less than about 5 millimeters. In addition, the length of flexible spring connector 74 is preferably less than about 20 millimeters.

In the embodiment shown in FIG. 4, flexible spring connector 74 comprises two concentric, oppositely wound springs 75, 76. Inner spring 75 is comprised of a single wire having an overall diameter of less than about 0.05 millimeters, which is wound in a counterclockwise direction. Outer spring 76 is comprised of a single wire having an overall diameter of less than about 0.05 millimeters, which is wound in a clockwise direction. Inner spring 75 is inserted into outer spring 76 to form flexible spring connector 74. Since springs 75 and 76 are oppositely wound, they are able to counteract each other when a twisting force is a applied. As a result, when the occluding bodies are attached to proximal and distal hubs 72, 73 (as described with respect to FIGS. 1A-1B), spring connector 74 will prevent the occluding bodies from rotating with respect to each other and to center connector 74. However, flexible spring connector 74 is still extremely flexible, while retaining the ability to transmit torque, push, and pull forces, and it is possible to rotate an occlusion device including flexible spring connector 54 during deployment.

Center assembly 70 also includes safety tether 77. As explained in detail with reference to FIGS. 2-3, safety tether 77 serves to further ensure the structural integrity of center assembly 70. Safety tether 77 connects proximal hub 72 to distal hub 73 and extends through the middle of flexible spring connector 74. (Methods of attaching safety tether 77 to proximal and distal hubs 72, 73 are identical to those discussed in detail with reference to FIG. 3.) Safety tether 77 may be comprised of any suitable material, including Nitinol, titanium, stainless steel or polymeric material. In addition, safety tether 77 may be comprised of a single wire or thread or safety tether 77 may be comprised of a multi-wire strand or cable or a multi-thread fabric braid.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. 

1. An occlusion device comprising: a first occluding body; a second occluding body; and a center assembly comprising a proximal hub attached to the first occluding body, a distal hub attached to the second occluding body, a flexible spring connector having a proximal end attached to the proximal hub and a distal end attached to the distal hub, and a safety tether having a proximal end attached to the proximal hub and a distal end attached to the distal hub, the safety tether extending through a middle of the flexible spring connector to connect the proximal hub to the distal hub, wherein the flexible spring connector comprises a plurality of springs extending between the proximal hub and the distal hub including a first spring coiled in a clockwise direction and a second spring coiled in a counterclockwise direction.
 2. The occlusion device of claim 1 wherein an overall diameter of the flexible spring connector is less than about 5 millimeters.
 3. The occlusion device of claim 1 wherein the safety tether comprises a wire.
 4. The occlusion device of claim 1 wherein the safety tether comprises a braided fabric.
 5. The occlusion device of claim 1 wherein the first spring and the second spring are concentric.
 6. An occlusion device comprising: a first collapsible support frame; a second collapsible support frame; a proximal hub connected to the first collapsible support frame; a distal hub connected to the second collapsible support frame; a spring connector providing a flexible connection between the proximal hub and the distal hub, the spring connector comprising a plurality of springs extending between the proximal hub and the distal hub including a first spring coiled in a clockwise direction and a second spring coiled in a counterclockwise direction; a tether having a proximal end attached to the proximal hub and a distal end attached to the distal hub, the safety tether extending through a middle of the spring connector and providing a safety connection between the proximal hub and the distal hub; and a first sheet attached to the first collapsible support frame.
 7. The occlusion device of claim 6 and further comprising a second sheet attached to the second collapsible support frame.
 8. The occlusion device of claim 6 wherein each of the first and second collapsible support frames includes a plurality of arms.
 9. The occlusion device of claim 6 wherein the first collapsible support frame is oriented relative to the second collapsible support frame to offset the arms of the first collapsible support frame from the arms of the second collapsible support frame.
 10. The occlusion device of claim 6 wherein an overall diameter of spring connector is less than about 5 millimeters.
 11. The occlusion device of claim 6 wherein the first spring and the second spring are concentric.
 12. The occlusion device of claim 6 wherein the tether comprises a wire.
 13. The occlusion device of claim 6 wherein the tether comprises a braided fabric. 